Historian Bettany Hughes will attempt to rescue Helen of Troy from "28 centuries of male fantasy" when the Guardian Hay festival begins in earnest today.

Hughes has written the first scholarly book about the mythical Helen, whose abduction by Paris caused the 10-year Trojan war. She will tell the festival that historians from Plutarch onwards have ignored Helen as a serious figure, preferring to reduce her to an object of sexual obsession. "She walks through history for 28 centuries holding up a mirror to the way men think of women."

Though Homer's account of Helen in the Iliad and the Odyssey is largely positive, said Hughes, by the 5th century BC she was already seen to embody dangerous female sexuality.

The dramatist Euripides called her a "bitch whore". A medieval writer called Joseph of Exeter wrote a condemnatory, but virtually pornographic epic about her in 1184, in which she "robs Paris of his semen". In Shakespeare's Lucrece she is a "strumpet", in Marlowe she "sucks forth my soul".

The Pre-Raphaelites made her an airhead, and in the 2004 film Troy she is "simpering, vacuous, empty and wishy-washy", according to Hughes. "Even Margaret Atwood's Penelopiad [from which the author reads tonight at Hay] makes her a brainless bitch, though at least she's got a character." According to Hughes, Homer's account points to a real historical background of powerful noblewomen in the Mycenean period, 500 years before he composed his poems at the start of the 7th century BC and passed on through oral tradition.

For example, in the Odyssey, Helen mixes a drug for the Greek veterans to make them forget painful memories of war. In the past 18 months, archeologists have found an "extraordinary percentage of opiates", according to Hughes, in vast dishes found on bronze age sites in Greece. That and other evidence suggest Helen's drug preparation in Homer could be a "500-year-old memory of a real Queen of Sparta".

She added: "I haven't found Helen of Troy, but this is the first time that anyone has realised that she exists beyond a multilayered fantasy object ... She relates to late-bronze age aristocratic women, who were in charge of much of palace society in the eastern Mediterranean and mainland Greece." In addition, Helen became important as a semi-divine figure. "From 600BC to AD 400 she was worshipped ardently as a quasi goddess," according to Hughes.

Adolescent girls venerated her in order to capture Helen's sexual power, singing homoerotic hymns describing each other's golden hair and delicate ankles. "This aspect of Helen has been completely ignored. People have wanted to keep her as a pretty-pretty, chocolate-box girl, instead of a fear-inspiring, venerated cult figure."

The Guardian Hay festival, dubbed "the Woodstock of the mind" by Bill Clinton, takes place in a town where books outnumber people 1,000 to one. This year, it occupies its biggest ever site, at 20 acres, compared with 13 acres in 2005. According to festival director Peter Florence, box office takings are up 25% on last year, with tickets for sold-out events doing a brisk black-market trade on eBay.